1. Field of the Invention
The present invention relates to a method of manufacturing an optical waveguide which is integrated on a transparent substrate and has electrodes along sides of the waveguide.
It also relates to the optical waveguide itself and to a use of the optical waveguide.
2. Background Information
EP 0304602 A2 discloses an arrangement in which an optical waveguide is integrated on a substrate. The substrate has electrooptical properties, i.e., it exhibits the Pockels effect, and is preferably formed from lithium niobate. If two optical waveguides on the substrate extend side by side and are separated by a short distance over a predetermined coupling length, an optical switch can be formed from them. To this end, a pair of electrodes for applying a switching voltage is disposed above the surface of the substrate in the area of the coupling region, and separated from said surface by a dielectric intermediate layer. In the coupling region, the distance between the two optical waveguides is chosen so that light is coupled between the optical waveguides as a function of the applied switching voltage. The optical waveguides are formed by diffusing into the substrate a material with a higher refractive index than that of the substrate.
This optical waveguide is disadvantageous in that the necessary diffusion processes are carried out at high temperatures, and that the dimensions of the substrates are limited by the available lithium niobate single crystals. In addition, lithium niobate has the disadvantage that its refractive index differs widely from that of the glass of a glass fiber. This causes losses when light is coupled from a glass-fiber optical waveguide to a lithium-niobate optical waveguide.